1. Field of the Invention
The present invention relates to composition and method for removing copper (Cu)-compatible resist, and more particularly, to composition and method for removing copper-compatible resist without the occurrence of corrosion.
2. Discussion of the Related Art
In general, a low resistance copper line is commonly utilized as an array line of an array substrate for a liquid crystal display (LCD) device, or as a circuit line of a semiconductor device to prevent resistance-capacitance (RC) delay. The copper line is usually formed through a photolithographic process incorporating fine pattern technology. The photolithographic process is well-known for fabricating semiconductor devices such as large scale integrated (LSI) circuits, very large scale integrated (VLSI) circuits, and display devices including LCD devices and plasma panel display (PDP) devices.
The LCD device makes use of optical anisotropy and polarization properties of liquid crystal molecules. The liquid crystal molecules have definite orientation alignment that results from their long thin shapes. The orientation of the liquid crystal molecules can be controlled by applying an electric field to the liquid crystal molecules. Accordingly, when an intensity of the applied electric field changes, the orientation of the liquid crystal molecules also changes. Since incident light through a liquid crystal material is refracted due to an orientation of the liquid crystal molecules resulting from the optical anisotropy of the aligned liquid crystal molecules, an intensity of the incident light can be controlled and images can be displayed.
Among the various types of LCD devices, active matrix LCD (AM-LCD) devices, in which thin film transistors (TFTs) and pixel electrodes connected to the TFTs are disposed in a matrix configuration, have been developed because of their high resolution and superior display of moving images.
An LCD device according to the related art is explained in detail with reference to FIGS. 1 and 2. FIG. 1 is a schematic plan view showing the related art LCD device. FIG. 2 is a schematic cross sectional view taken along a line II-II of FIG. 1.
As shown in FIGS. 1 and 2, a gate line 14 is formed on a substrate 10 along a first direction. A data line 26 crosses the gate line 14 along a second direction perpendicular to the first direction to define a pixel region P. A thin film transistor (TFT) or switching device T is located at a crossing of the gate line 14 and the data line 26 and is connected to the gate and data lines 14, 26.
A gate insulating layer 16 is formed on the gate electrode 12. A semiconductor layer 19, which is formed by subsequently depositing intrinsic amorphous silicon as an active layer 18 and impurity amorphous silicon as an ohmic contact layer 20, is deposited on the gate insulating layer 16 over the gate electrode 12. Source and drain electrodes 22, 24 are formed on the semiconductor layer 19. There is a space between the source and drain electrodes 22, 24 that form a channel exposing the portion of the active layer 18. The source electrode 22 is connected to the data line 26. The gate electrode 12, the semiconductor layer 19, and the source and drain electrodes 22, 24 constitute the TFT T.
Moreover, a passivation layer 28 is formed on the TFT T and has a drain contact hole 29 that exposes a portion of the drain electrode 24. In addition, a pixel electrode 30 is formed on the passivation layer 28 in the pixel region P and is connected to the drain electrode 24 via the drain contact hole 29. The pixel electrode 30 may be selected from one of the transparent conductive materials consisting of indium tin oxide (ITO), indium zinc oxide (IZO) and indium tin zinc oxide (ITZO).
In the multi-layered structure of the substrate 10, the metallic layers such as the gate line 14, the data line 26 and the TFT T may be selected from the metallic materials having a low resistance. In addition, the low resistance properties of the metallic materials are more typically required for large size display devices. Among them, copper is considered as a typical low resistant metallic material.
Next, an explanation of a photolithography process according to the related art will be given below. FIGS. 3A to 3C are schematic cross sectional views showing a patterning process including a photolithography process and an etching process taken along a line II-II of FIG. 1. Specifically, the patterning process is utilized for forming the gate line 14 and the gate electrode 12 or a gate pattern.
In FIG. 3A, a metal layer 11 is formed by depositing copper on the substrate 10. Next, a photoresist layer 40 is formed by coating a photoresist material on the metal layer 11. The photoresist material may be classified into a positive type in which an exposed portion of the photoresist material is removed by developing, and a negative type in which an exposed portion of photoresist material is left after developing. For example, the photoresist material in FIGS. 3A to 3C belongs to the positive type.
To perform the photolithography process, a mask M, which has a transmissive portion E and a shielding portion F, is disposed over the photoresist layer 40. At this time, the portion of the photoresist layer 40, which corresponds to the shielding portion F of the mask M, is a photoresist pattern.
Next, an actinic radiation, which is a specific radiation capable of inducing a chemical reaction, is irradiated onto the photoresist layer 40 over the substrate 10 through the mask M. In fact, the actinic radiation is irradiated onto the portion of the photoresist layer 40 corresponding to the transmissive portion E of the mask M. Specifically, the actinic radiation may be selected from high energy radiations such as ultra violet rays, electron beam, X-rays, or the like. In the step of exposing, the actinic radiation reaches the photoresist layer 40 through the transmissive portion E of the mask M to change the properties of the photoresist layer 40.
After the step of exposing, the photoresist layer 40 has a first portion EE with changed properties of the matter and a second portion FF with unchanged properties of the matter. In other words, the first and second portions EE and FF of the photoresist layer 40 correspond to the transmissive and shielding portions E and F of the mask M, respectively. Since the first and second portions EE and FF of the photoresist layer 40 are determined by the patterns of the mask M such as the transmissive and shielding portions E and F, they may be called a potential phase for the mask M. When the step of exposing is completed, a step of developing for pattering the photoresist layer 40 is performed as follows.
Referring to FIG. 3B, the second portion FF of the photoresist layer 40 of FIG. 3A is patterned into a photoresist pattern 42 through developing. The photoresist pattern 42 corresponds to the shielding portion FF of the mask M of FIG. 3A. Therefore, the portion of the metal layer 11 is exposed except for the portion covered by the photoresist pattern 42.
Next, as shown in FIG. 3C, in order to form a metal pattern, the exposed portion of the metal layer 11 is etched utilizing the photoresist pattern 42 as etching barrier means. Specifically, the metal pattern may be utilized as the gate line 14 and the gate electrode 12 as shown in FIG. 1. Although not shown, a step of removing the photoresist pattern 42 by utilizing a stripping agent is performed after the step of patterning the metal layer.
The above-discussed photolithography process is an essential process to form the metal line and electrode for the array substrate of the LCD device. These metal line and electrode are properly selected from low resistant metallic materials in light of signal applying speed of them. Recently, copper has been regarded as the typical low resistant metallic material.
However, the use of copper in this regard has some disadvantages in that, for example, an oxidation reaction is caused by exposure of the copper line to room temperature. Moreover, when copper of about 99.9999% is exposed to room temperature, it may be easily oxidized. Further, the oxidized copper line may easily be corroded by a stripping agent for removing the photoresist pattern. Because of these oxidation and corrosion issues, the corrosion of the copper line may occur relatively fast. Moreover, the copper line is also easily corroded by conventional solvents that are utilized to remove the resist pattern during the photolithographic process. Accordingly, solvent compositions that include a corrosion inhibitor for preventing corrosion of copper should be utilized, as demonstrated in U.S. Pat. Nos. 5,417,877 and 5,556,482, which are hereby incorporated by reference. Examples of possible corrosion inhibitors include mono-ethanol-amine (MEA) as a preferred amine. A specific amount of corrosion inhibitor is required so that removing properties of the inhibitor can be ensured without degradation. Generally, the basic elements of the composition for removing a copper-compatible resist include an amine compound solvent, a polar solvent and a glycol group solvent.
FIG. 4 is a scanning electron microscopy (SEM) image showing a corrosion state of a copper line by a composition including a monoethanolamine according to the related art. As shown in FIG. 4, the corrosion of the copper line severely occurred in case of utilizing the amine compound solvent including primary amine such as the mono-ethanol amine.
FIG. 5 is a SEM image showing a corrosion state between a copper line and a metal layer underneath the copper line in case of utilizing the stripping agent according to the related art. In FIG. 5, when the stripping agent did not contain a corrosion inhibitor, the corrosion between the copper line and the metal layer situated beneath the copper line is caused after stripping using the stripping agent.
In general, the corrosion between the copper line and the metal layer severely occurs by a galvanic phenomenon between the copper line and the metal layer in case of including about 0.1 to 3.0% by weight of water even if the corrosion of the copper line is not caused by the amine compound solvent.